Construction of a Test Chamber for Human Infrasound Exposure

The report describes the construction of an infrasound test chamber, in which subjects can be exposed to controlled infrasound signals. The infrasound is produced by 16 electrodynamic loudspeakers, mounted in one wall of the 16 m 3 chamber. The maximum sound pressure level that can be obtained is 125 dB rms in the frequency range 0.05 Hz–30 Hz. At a level of 120 dB the 2nd and 3rd harmonic distortions are below 1%. The system does not utilize any acoustical resonances, thus giving a flat frequency response. In this way it is possible to reproduce a real environmental infrasound signal recorded on tape. For the purpose of experiments of longer duration, the room is equipped with a ventilating system, which gives sufficient air exchange for 3 persons. When in use, this system increases the lower limiting frequency to 0.3 Hz.